There is no good numerical correlation between these two methods.  They impart significantly different amounts of energy to the soil for compaction in the lab.  

I would not expect to see as great a difference as you have noted.  Usually the diffence between standard and modified values is more on the order of 3 to 5 percent.

The standard Proctor is more often specified for the material you are encountering.  The reason for this is that the compactive energy needed for this type of material is dynamically less and the material responds better to a kneading form of compaction (sheepsfoot roller vs. vibratory compactor, for instance).

Review the results carefully, though.  Something appears to be screwy.

Ron....... Thanks a whole bunch.... I had heard there was a 5% difference but have never seen literature or competent discussion to back up the numbers. I will be tlaking to the GC in the morning and want to see the backup for both tests..... Thanks again.

Did ASTM renumber these test specifications?  I seem to remember different ASTM numbers for Standard and Modified Proctor tests.

The ASTM Nos are correct according to my Vol.04.08, but its a bit old, 1993.  On the original subject, I found an interesting article at www.stratageotech.com titled Engineering Fills and Compactions. They have an interesting discussion which may be ammunition for compaction under a building.

Nope...those have been the numbers for at least 25 years that I know of.

FYI:

D698 is generally used for "thin" fills beneath structures.

D1557 is used for airport runways, highways and "deep" fills beneath buildings.  Ron is right about the amount of energy - D1557 involve a lot more energy imparted to the soil than D698.

I usually (in Toronto) for Granular A and B fills used 97% Modified = 100% Standard.  Of course, material type and other factors come into play. I typically use standard proctors in embankment constrution for roads, general fills (such as backfills to basement walls, etc.)  I use modified for fills under foundations (such as paper machines, compressors, etc.).  Keep in mind that most contractors will "scoff" at a standard compaction requirement but when they see Modified, they usually take it a bit more seriously.  Psychological.

Might want to check out Monihan's book on Compaction. (He is/was a professor at NJ Institute of Technology.  It is rather a good book.  He proferred that the Modified Proctor is known as the "Blister Test" - I happen to like calling it the "Hernia Test".

Best regards.

Local practices - based on available materials, weather and what has proved successful on similar projects - are important.  For BigH, using the modified Proctor may make sense under buildings because his Toronto-area projects use a lot of granular fill.  This makes sense because the materials are easy to compact to this standard.  Here in central Texas, we do use modified Proctor on crushed limestone base material as fill beneath buildings; but low PI clays are also commonly used as fill along the coast (Houston, Corpus Christi, Brownsville.)  We have to be careful to avoid overcompaction in these materials!

The Old Navy Design Manual on Soil mechanics had correlation equations for estimating standard and modified proctor maximum dry density values.  The equation for estimating standard proctor maximum dry density in English units is:
gammad max = 130.8-0.82*LL + 0.21*PI

Based on data given in the manual, I developed an equation relating the Modified Proctor maximum density to the Standard Proctor value.  The D1557 density is about 97.5 percent of the D698 value + 10.75 pounds.  In other words, if a soil has a D698 dry density of 100 pounds, the D1557 value would be about 0.975(100) + 10.75 = 108 pcf.

This equation is only applicable for soils with appreciable plasticity without a lot of sand or gravel particles.  I never use the equations for PI values less than 10.

An excellent rule of thumb in determining what degree of compaction is possible to achieve is that if the natural water content of soils is greater than about 2 percent wet of optimum, you will not be able to achieve 100 percent of Standard Proctor D698 dry density.  If the natural water content is wetter than 4 percent over optimum, you will not be able to obtain more than 95 percent of D698A

Comparisons between the D-698 & D-1557 results must be made with caution. The type of soil (GM, SC, CL, CL-ML) has a lot to do with the final results as much as the actual gradation(GP vs GW).  In Western Colorado, I deal with a lot of CL-ML and the difference between the 2 methods can be as high as 17 pcf & 8 % OMC.  The 15% difference is real for some soils.  

By comparison, I have seen a very well graded Road Base (ABC) have less than 1 pcf  & 1/2 % OMC difference. I considered this particular ABC to truly be 'Select' as is compacted quite easily and proved to be very stable.  Wish we had a lot more of it.

It is important to remember that fills will settle and some silty clay soils (CL-ML) which have been compacted to 95% D-698 @ OMC may experience unacceptable settlement in deeper fills.  BUT, 90% of D-1557 @ OMC may not experience unacceptable settlement.   UNDERSTAND THE SOILS & THE CONDITIONS.

I have a related question. Can someone explain the procedure and significance of running a "one point proctor" in the field and adjusting optimum weight prior to reporting % compaction on material that is essientially uniform.

Mwhite,
As the others were saying, I have also observed differences between the two tests on granular soils of between 3 and 5% depending on gradation and other soil properties, and of course, quality of testing performed.  I had this same question before myself and I decided to conduct a little comparison testing program a while back since I was getting mixed answers from the techs and other engineers around the area...(although in this forum I typically get very good answers!)

I already have the correlation between the proctor standard and the modified proctor. If you mail me the proctor curve, I will return you the modified curve, for any kind of material.
I am writing a book about the Proctor test and other laboratories testes. These is part of my researches, and I would like publish it in these year.

drfefefe

Is there a way of obtaining a copy of your research?

Keystone Retaining Wall Systems has interesting pdf file available on-line that explains D698 vs D1557.

www.bestblock.com/media/new.media/ kstechnotes/technote_pdfs_BB/soil_dens.pdf

Also, did we ever get word on drfefefe's research?

Techmaximus